Simulation study of interaction between runaway electron generation and resistive MHD modes over avalanche timescaleSimulation study of interaction between runaway electron generation and resistive MHD modes over avalanche timescale
Runaway electron generation is simulated using a reduced magnetohydrodynamic (MHD) model that couples runaway generation process and resistive kink modes. It is shown that the concentration of runaway current near the magnetic axis is limited by the presence of sawtooth-like activity, which radially redistributes seed electrons simultaneously with a modification of the ohmic current profile to maintain the central safety factor above unity. The profile of runaway generation rate is also modified, where the peak location of Dreicer generation rate is shifted radially outwards and the resistive kink hinders a feedback mechanism that causes the current concentration in the plasma center. The flat profile of seed electrons is inherited by the avalanche growth. Flat current and q profiles over the beam radius are observed at the runaway current plateau on the avalanche timescale.